Shoulder endoprosthesis for fractures of the upper end of the humerus

ABSTRACT

A shoulder endoprosthesis for fractures of the upper end of the humerus, comprising a humeral stem, adapted to be accommodated in an intramedullary canal of the humerus and provided with multiple longitudinal ribs, and a humeral proximal part, which is suitable to couple to one end of the stem, is provided with a plurality of lateral fins and has, at an upper end, a portion for engagement with a humeral head which is suitable to reconstruct the head of the humerus of the patient.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a shoulder endoprosthesis forfractures of the upper end of the humerus.

[0002] It is known that among the various kinds of fracture of the upperend of the humerus four-part fractures are the most severe and oftenrequire surgical treatment when the fragments of the fracture aremutually dislocated.

[0003] In a four-part fracture the muscles play a key role in thepathophysiology of this type of fracture, since they pull in differentdirections on each fragment of the fracture. As shown in FIG. 1, thediaphysis 1, the fragments of the inferior tuberosity 2, the uppertuberosity 3 and the humeral head 4 are separated one another and thefracture is not simple. Conservative treatment by surgical reduction isnot satisfactory and very often causes pseudarthrosis or necrosis of thehumeral head.

[0004] Accordingly, in these cases the only possible treatment thatallows to recover complete mobility and eliminate pain is jointreplacement.

[0005] Most surgical procedures that use shoulder joint prostheses arethe consequence of fractures.

[0006] Currently known shoulder prostheses are mainly cemented and haveholes in the proximal-lateral part in order to allow fixation of thetuberosities. However, the location of said holes makes it difficult toachieve stable fixation of the tuberosities; accordingly, fragmentconsolidation is often not achieved and patients complain of continuouspain and unsatisfactory mobility of the joint.

[0007] With most of the currently known shoulder prostheses, once thecement has set it is not possible to correct retroversion and thereforeposition the prosthesis appropriately.

SUMMARY OF THE INVENTION

[0008] The aim of the present invention is to provide a shoulderendoprosthesis which can be applied in the case of multiple fractureswithout requiring bone cement.

[0009] Within the scope of this aim, an object of the present inventionis to provide a shoulder endoprosthesis which allows to restore humerallength and correct retroversion.

[0010] Another object of the present invention is to provide a shoulderendoprosthesis which allows to fix the tuberosities to the diaphysis aswell as to the prosthesis.

[0011] Another object of the present invention is to provide a shoulderendoprosthesis which allows to reposition the tuberosities with thecorrect tension and in the correct seat.

[0012] Another object of the present invention is to provide a shoulderendoprosthesis which is highly reliable, relatively easy to manufactureand at competitive costs.

[0013] This aim and these and other objects which will become betterapparent hereinafter are achieved by a shoulder endoprosthesis forfractures of the upper end of the humerus, characterized in that itcomprises a humeral stem, which is suitable to be accommodated in anintramedullary canal of the humerus and is provided with multiplelongitudinal ribs, and a humeral proximal part, which is suitable tocouple to one end of said stem, is provided with multiple lateral finsand has, at an upper end, a portion for engagement with a humeral headwhich is suitable to reconstruct the head of the humerus of the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Further characteristics and advantages will become betterapparent from the description of preferred but not exclusive embodimentsof the shoulder endoprosthesis according to the present invention,illustrated only by way of non-limitative example in the accompanyingdrawings, wherein:

[0015]FIG. 1 is a perspective view of a four-part fracture of the upperend of the humerus;

[0016]FIG. 2 is an exploded view of the shoulder endoprosthesisaccording to the present invention;

[0017]FIG. 3 is a front view of the humeral proximal part thatconstitutes one of the components of the endoprosthesis shown in FIG. 2;

[0018]FIG. 4 is a plan view of the humeral stem, accommodated in theintramedullary canal of the humerus;

[0019]FIG. 5 is a schematic view of the insertion of the endoprosthesisaccording to the invention in the humerus; and

[0020]FIG. 6 is a view of a second embodiment of the humeral head whichconstitutes a component of the endoprosthesis according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] With reference to the figures, and particularly to FIGS. 2 to 6,the endoprosthesis according to the present invention, generallydesignated by the reference numeral 10, comprises a humeral stem 15designed to be inserted in the intramedullary canal of the humerus,which is designated by the reference numeral 11 in FIGS. 4 and 5.

[0022] The second component of the endoprosthesis according to theinvention is constituted by the humeral proximal part 16, designed tocouple to the humeral stem 15 at one end and to a humeral head 17 at theopposite end. The humeral head 17 constitutes the third component of theendoprosthesis 10 and is conveniently constituted, for example, by aspherical portion.

[0023] In detail, the humeral stem 15 is a conical tubular element whichhas, on its lateral surface, longitudinal ribs 18 which are suitable topenetrate for a few tenths of a millimeter in the cortex of the humerus11, ensuring excellent primary and secondary stability against rotation.

[0024] Conveniently, the humeral stem 15 is made for example of titaniumalloy and tapers gently with a total angle of for example 2°.

[0025]FIG. 4 is a plan view of the insertion of the humeral stem 15 inthe intramedullary canal of the humerus 11, with the longitudinal ribs18 which engage the internal surface of the intramedullary canal of thehumerus 11, allowing stable fixation of the humeral stem 15.

[0026] The second component of the endoprosthesis according to theinvention, i.e., the humeral proximal portion 16, which is also forexample made of titanium alloy, can be provided in different sizes, eachhaving a different length.

[0027] The humeral proximal portion 16 is formed by a body which isshaped so as to engage, at one end, the conical end portion 19 of thehumeral stem 15, and has, at the opposite end, a protruding conicalportion 20 which is suitable to engage an appropriately provided seat 21formed in the humeral head 17.

[0028] Conveniently, the conical portion 20 is angled with respect tothe axis of the proximal part 16 and therefore of the stem 15.

[0029] Preferably, the angle of the conical portion 20 is approximately135°.

[0030] The lateral surface of the proximal part 16 has a plurality offins 23 which are suitable to allow fixation of the tuberosities in thebone in order to afford stable anchoring.

[0031] The fins 23 have holes 24 which allow to fix wires to thetuberosities.

[0032] Additional holes 25 for anchoring wires to the tuberosities arefurther provided in the anterior portion of the proximal part 16.

[0033] The holes 25 are through holes, as shown in the front view ofFIG. 3.

[0034] The seat 21 formed in the humeral head 17 and suitable to allowthe engagement of the conical portion or neck 20 can be convenientlyprovided with an axis which is inclined with respect to the axis ofsymmetry 32 of the humeral head 17.

[0035] In this case, the axis of the seat designated by the referencenumeral 31 is substantially inclined with respect to the axis ofsymmetry 32. This allows better adaptation of the humeral head 17 to theanatomy of the proximal epiphysis.

[0036]FIG. 6 illustrates two different inclinations of the axis 31.

[0037] Essentially, the anchoring of the prosthesis according to theinvention to the humerus is very simple, since it does not require theuse of bone cement, and allows to fix the two tuberosities by usingwires.

[0038] The humeral stem 15 is further inserted in the intramedullarycanal of the humerus 11, also without using bone cement, and thelongitudinal ribs 18 allow its stable anchoring.

[0039] In practice it has been observed that the shoulder endoprosthesisaccording to the invention fully achieves the intended aim, since itallows to reduce the fracture and restore joint function with a fullynatural anchoring to the bone.

[0040] The endoprosthesis according to the invention is susceptible ofnumerous modifications and variations, all of which are within the scopeof the inventive concept. All the details may furthermore be replacedwith other technically equivalent elements.

[0041] In practice, the materials employed, so long as they arecompatible with the specific use, as well as the dimensions, may be anyaccording to requirements and to the state of the art.

[0042] The disclosures in Italian Patent Application No. M12000A000122from which this application claims priority are incorporated herein byreference.

What is claimed is:
 1. A shoulder endoprosthesis for fractures of theupper end of the humerus, comprising a humeral stem, which is suitableto be accommodated in an intramedullary canal of the humerus and isprovided with multiple longitudinal ribs, and a humeral proximal part,which is suitable to couple to one end of said stem, is provided with aplurality of lateral fins and has, at an upper end, a portion forengagement with a humeral head which is suitable to reconstruct the headof the humerus of the patient.
 2. The endoprosthesis according to claim1 , wherein said humeral stem is constituted by a conical tubularelement, said plurality of longitudinal ribs being formed on an outersurface of said stem.
 3. The endoprosthesis according to claim 1 ,wherein said humeral proximal part has multiple through holes arrangedin an anterior region thereof.
 4. The endoprosthesis according to claim1 , wherein said plurality of lateral fins of said humeral proximal partare each provided with a hole.
 5. The endoprosthesis according to claim1 , wherein said portion for the engagement of said humeral proximalpart with said humeral head is frustum-shaped and angled with respect toan axis of simmetry of said humeral head.
 6. The endoprosthesisaccording to claim 5 , wherein said humeral head is a spherical portioninside which there is, at a center, a seat for engagement with saidhumeral proximal part.
 7. The endoprosthesis according to claim 6 ,wherein said seat has an axis which is substantially inclined withrespect to the diametrical axis of symmetry of said spherical portion.